1. Field of the Invention
The present invention relates to cannulas used in connection with medical procedures and techniques, more particularly to cannulas used in procedures and techniques involving the eye and eye surgery (e.g., retinal tear or detachment surgery, macular hole surgery), as well as methods related thereto.
2. Background
Retinal tears can occur when the vitreous, a clear gel-like substance that fills the center of the eye, pulls away from the retina thereby leaving behind a tear or hole in the retina. Rhegmatogenous retinal detachments can result if the retinal breaks (i.e., tears or holes in the retina) are not treated. With retinal breaks, fluid from the vitreous apparently seeps through the retinal break and accumulates under the retina. The degree of detachment is measured by the volume of subretinal fluid present as well as the area of the retina involved. Some symptoms of retinal detachment include the presence of floaters, flashes, shadows or blind areas, decreased visual acuity and metamorphopsia.
A number of techniques may be employed for treating retinal detachments, including using a scleral buckle, pneumatic retinopexy, cryopexy (i.e., freezing) and photocoagulation using a laser or xenon arc light source. These techniques may be used alone or in combination with each other to treat the retinal detachments. For example, a combination of a scleral buckle and photocoagulation may be used in some cases. Alternatively, retinal tears with little or no nearby detachment may be treated using photocoagulation or cryopexy.
Using a laser in the photocoagulation technique, the retinal break is surrounded with one or more rows of a plurality of laser burns or laser heat spots. These laser bums or heat spots produce scars which prevent fluid from passing through and collecting under the retina. In the photocoagulation procedure, a gas is exchanged with the vitreous fluid being aspirated from within the eye so that the gas is intraocular when performing photocoagulation.
During vitreoretinal surgery, intraocular pressure is maintained by infusing a fluid, such as a buffered saline solution, from an elevated IV bottle into the eye through a cannula. Often the surgical procedures will call for air to be infused through the cannula while the fluid is being drained and/or aspirated through a second port or means. Recent findings discuss the potential for damage to the retina occurring during the fluid-air exchange.
Thus, it would be desirable to have improved devices, systems and methods for infusing a gas, particularly air, to a patient""s eye during eye surgery procedures. It would be particularly desirable to have improved devices, systems and methods for infusing air or other gas to a patient""s eye during surgery so as to limit or avoid the potential for damage to the retina as compared to prior art devices, systems, methods or techniques.
There has now been produced new devices and methods that enable infusing air or other gases to be infused into a patient""s eye during surgical procedures (e.g. macular hole surgery) that minimize or avoid damage to the retina during the fluid-air exchange process, particularly when infusing a gas into the eye.
More particularly, the present invention features a non-traumatic cannula for use in connection with eye surgery, such as retinal tear and/or detachment surgery. The non-traumatic cannula of the present invention is particularly configured so as to minimize or avoid the potential for damage to the retina when infusing air or a gas therein. The invention also features related methods for infusing air during eye surgical procedures as well as methods for treating a retinal tear or detachment.
The methods of the invention generally comprise diffusively flowing a fluid into the ocular cavity of a patient""s eye, typically during an eye surgery procedure. More particularly, the methods include providing a non-traumatic cannula having a lumen for transporting the fluid to be infused. One end of this non-traumatic cannula, which is in fluid communication with the lumen, includes a means for diffusing or disrupting the flow of fluid from the non-traumatic cannula so there is an infusion of fluid into the eye, which infusion is non-traumatic with respect to the retina. Typically, the fluid is in the form of a gas, although for many applications a liquid may be diffusively applied to a patient eye.
Preferred non-traumatic cannulas of the present invention include a fluid exit portion that includes a tubular member having an interior passage fluidly coupled to a fluid source. One end of the tubular member further includes a means or mechanism for diffusively infusing the fluid therein from the end of the tubular member.
The mechanism by which the fluid is diffusively infused is adapted for mechanical deflecting or re-directing the flow of fluid, creating turbulent flow from the tubular member end or porous diffusion of the fluid through the tubular member end. In that way, the flow into the ocular cavity is diffusive. The mechanism for mechanical deflecting of the fluid flow includes one of a baffle member, providing a cannula having a sealed end with opposed elongated slots in a side of the tubular member and a tubular member end having a multiple slotted end with a deflecting member disposed in the end.
The term xe2x80x9cdiffusive flowxe2x80x9d of fluid or other similar terms to describe fluid exiting a device of the invention typically indicates the fluid is flowing in a turbulent, non-laminar manner. See McGraw-Hill Encyclopedia of Science and Technology (McGraw-Hill), incorporated herein by reference, for discussions of the terms turbulent and laminar. Preferably, fluid diffusively flowing out of a device of the invention onto a patient eye will have a Reynolds number (pvd/xcexc) of greater than about 2,000, more typically greater than 2,400 or 2,500, more preferably a Reynolds number of greater than 2,800, 2,900 or 3,000.
Other aspects and embodiments of the invention are discussed infra.